Generally, in the case where an object such as a hinge, a sliding wheel, a bracket, a flanged sleeve and the like is to be attached to the external side of a panel type structure, a hole is drilled at the fastening portion of the panel member or wall in order to insert a screw, a bolt or a blind rivet, and then, the object to be attached is fastened using the above mentioned means. However, in the case where the panel member of the fastening portion is too thin to accommodate a number of screw pitches large enough to provide a proper fastening strength, an additional reinforcing plate has to be put to the other side of the structure where an object is to be attached. In this case the additional reinforcing plate should be thick enough to provide a proper withstanding strength, and a threaded fastening hole or a riveting hole has to be formed on the additional reinforcing plate.
Further, in the case where a structure is too thick to allow a tapping through the structure as in the case of a wall, and in the case where the hardness of the structure is too high to allow a tapping operation, the above mentioned kind of an additional aiding plate is required.
However, there is the problem that, if the other side (or inner side) of the structure is in a closed state, or has a limited space to such extent that the other side is not approachable by means of a hand or a tool, then the above mentioned additional reinforcing plate or aiding plate cannot be installed, as well as other kinds of fastening means.
In an effort to overcome such problems, there have been proposed a plurality of devices using divided washers, nuts and guide strings. For example, a fastening hole having a diameter large enough to receive a nut is provided, and a washer having an outside diameter larger than the inner diameter of the fastening hole is divided into several pieces. Then the nut and the divided pieces of the washer are connected by means of a guide string, and then, they are inserted through the fastening hole. The nut and the divided pieces of the washer are constituted such that if the guide string is pulled forward, they are assembled into the complete original form at the other side of the structure. Thus the nut and the washer are secured at the other side of the structure so that an object to be attached could be fastened by means of a fastening aid such as a bolt and the like.
Another device is constituted such that a relatively large insertion hole is drilled through the structure, and a divided washer having an outside diameter larger than the diameter of the insertion hole is inserted into the insertion hole. The divided washer is provided with a plurality of fastening holes on a region coming within the boundary of the insertion hole.
This device is useful for the case where the object to be attached requires a plurality of fastening holes.
However, if the fastening holes of the object to be attached are too widely dispersed to such extent that the fastening holes of the object are located too outwardly from the boundary of the insertion hole, then the device is of no use.
Therefore, if a plurality of insertion holes on the structure are to be used for fastening the object, it is necessary that a plurality of separate divided washers have to be provided at the other side of the structure at positions corresponding to a plurality of the insertion holes. However, in the case where it is required that the insertion holes are to be adjacently located one another, there is the possibility that the divided washers can be overlapped partially, and that the attachment of the object is not strong enough due to the narrowed area of the array of the fastening holes.